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ScienceAges 16-18

Acids, bases & the pH scale

Use the 0–14 pH scale, indicators and neutralisation reactions to classify acidic, neutral and alkaline solutions. Review suitability for your learners before teaching.

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Worksheet StudioPractice pack · Ages 16-18

Acids, bases & the pH scale

Take your time. Show your thinking.

  1. 1. What weak organic acid is found naturally in lemons, limes and oranges: citric acid or sulfuric acid?

    pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution

  2. 2. In an acid–base titration, which piece of graduated glassware with a tap at the bottom is used to measure the exact volume of acid or alkali added: a burette or a beaker?

    pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution

  3. 3. What weak organic acid gives vinegar its sour taste: ethanoic (acetic) acid or nitric acid?

    pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution

  4. 4. Which type of salt is always produced by reactions of sulfuric acid (H₂SO₄): a sulfate or a nitrate?

    pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution

  5. 5. What is the chemical test that confirms a gas is oxygen (O₂): it relights a glowing wooden splint, or it turns limewater milky?

    pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution

  6. 6. Which ion is released by all Arrhenius acids when dissolved in aqueous solution: hydrogen ions (H⁺) or hydroxide ions (OH⁻)?

    pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution

  7. 7. On the standard pH scale (0 to 14) at 25 °C, what is the pH of a neutral solution such as pure water: 7 or 0?

    pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution

  8. 8. Does an alkaline (basic) solution (such as sodium hydroxide or soapy water) have a pH greater than 7 or less than 7?

    pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution

  9. 9. What colour does blue litmus paper turn when dipped into an acidic solution: red or blue?

    pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution

  10. 10. What are the two products formed when an acid reacts with an alkali in a neutralisation reaction: a salt and water, or hydrogen and carbon?

    pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution

  11. 11. Because the pH scale is logarithmic, a decrease of 1 pH unit (e.g. from pH 4 to pH 3) means the H⁺ ion concentration increases by a factor of: 10 or 2?

    pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution

  12. 12. What colour is phenolphthalein indicator in an acidic solution vs a basic solution: colourless in acid and pink in alkali, or blue in both?

    pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
12 questions · Seed 104729 · Age guidance, not curriculum certification
View the answer key
Worksheet StudioAnswer key · Ages 16-18

Acids, bases & the pH scale

Answers and reasoning. Review before teaching.

  1. 1. What weak organic acid is found naturally in lemons, limes and oranges: citric acid or sulfuric acid?

    Citric acid

    Citrus fruits contain citric acid.

  2. 2. In an acid–base titration, which piece of graduated glassware with a tap at the bottom is used to measure the exact volume of acid or alkali added: a burette or a beaker?

    Burette

    A burette delivers variable volumes accurately to within 0.05 cm³.

  3. 3. What weak organic acid gives vinegar its sour taste: ethanoic (acetic) acid or nitric acid?

    Ethanoic (acetic) acid

    Vinegar is a dilute aqueous solution of ethanoic (acetic) acid.

  4. 4. Which type of salt is always produced by reactions of sulfuric acid (H₂SO₄): a sulfate or a nitrate?

    Sulfate

    Sulfuric acid forms sulfate salts; nitric acid forms nitrates; hydrochloric acid forms chlorides.

  5. 5. What is the chemical test that confirms a gas is oxygen (O₂): it relights a glowing wooden splint, or it turns limewater milky?

    It relights a glowing wooden splint

    Pure oxygen supports rapid combustion and relights a glowing splint.

  6. 6. Which ion is released by all Arrhenius acids when dissolved in aqueous solution: hydrogen ions (H⁺) or hydroxide ions (OH⁻)?

    Hydrogen ions (H⁺)

    Acids produce aqueous hydrogen ions (H⁺ / H₃O⁺) in water.

  7. 7. On the standard pH scale (0 to 14) at 25 °C, what is the pH of a neutral solution such as pure water: 7 or 0?

    7

    A pH of 7 is neutral, with equal concentrations of H⁺ and OH⁻ ions.

  8. 8. Does an alkaline (basic) solution (such as sodium hydroxide or soapy water) have a pH greater than 7 or less than 7?

    Greater than 7

    Alkalis (soluble bases) have pH values above 7 (from 7 to 14).

  9. 9. What colour does blue litmus paper turn when dipped into an acidic solution: red or blue?

    Red

    Acids turn blue litmus paper red.

  10. 10. What are the two products formed when an acid reacts with an alkali in a neutralisation reaction: a salt and water, or hydrogen and carbon?

    A salt and water

    Acid + Alkali → Salt + Water (H⁺ + OH⁻ → H₂O).

  11. 11. Because the pH scale is logarithmic, a decrease of 1 pH unit (e.g. from pH 4 to pH 3) means the H⁺ ion concentration increases by a factor of: 10 or 2?

    10

    pH = −log₁₀[H⁺], so each whole unit decrease represents a tenfold increase in [H⁺].

  12. 12. What colour is phenolphthalein indicator in an acidic solution vs a basic solution: colourless in acid and pink in alkali, or blue in both?

    Colourless in acid and pink in alkali

    Phenolphthalein is colourless below pH 8.2 and turns pink-magenta in alkaline solutions.

12 questions · Seed 104729 · Age guidance, not curriculum certification
Worksheet StudioPractice pack · Ages 16-18

Acids, bases & the pH scale

Take your time. Show your thinking.

  1. 1. What weak organic acid is found naturally in lemons, limes and oranges: citric acid or sulfuric acid?

    pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution

  2. 2. In an acid–base titration, which piece of graduated glassware with a tap at the bottom is used to measure the exact volume of acid or alkali added: a burette or a beaker?

    pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution

  3. 3. What weak organic acid gives vinegar its sour taste: ethanoic (acetic) acid or nitric acid?

    pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution

  4. 4. Which type of salt is always produced by reactions of sulfuric acid (H₂SO₄): a sulfate or a nitrate?

    pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution

  5. 5. What is the chemical test that confirms a gas is oxygen (O₂): it relights a glowing wooden splint, or it turns limewater milky?

    pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution

  6. 6. Which ion is released by all Arrhenius acids when dissolved in aqueous solution: hydrogen ions (H⁺) or hydroxide ions (OH⁻)?

    pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution

  7. 7. On the standard pH scale (0 to 14) at 25 °C, what is the pH of a neutral solution such as pure water: 7 or 0?

    pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution

  8. 8. Does an alkaline (basic) solution (such as sodium hydroxide or soapy water) have a pH greater than 7 or less than 7?

    pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution

  9. 9. What colour does blue litmus paper turn when dipped into an acidic solution: red or blue?

    pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution

  10. 10. What are the two products formed when an acid reacts with an alkali in a neutralisation reaction: a salt and water, or hydrogen and carbon?

    pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution

  11. 11. Because the pH scale is logarithmic, a decrease of 1 pH unit (e.g. from pH 4 to pH 3) means the H⁺ ion concentration increases by a factor of: 10 or 2?

    pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution

  12. 12. What colour is phenolphthalein indicator in an acidic solution vs a basic solution: colourless in acid and pink in alkali, or blue in both?

    pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
12 questions · Seed 104729 · Age guidance, not curriculum certification
Worksheet StudioAnswer key · Ages 16-18

Acids, bases & the pH scale

Answers and reasoning. Review before teaching.

  1. 1. What weak organic acid is found naturally in lemons, limes and oranges: citric acid or sulfuric acid?

    Citric acid

    Citrus fruits contain citric acid.

  2. 2. In an acid–base titration, which piece of graduated glassware with a tap at the bottom is used to measure the exact volume of acid or alkali added: a burette or a beaker?

    Burette

    A burette delivers variable volumes accurately to within 0.05 cm³.

  3. 3. What weak organic acid gives vinegar its sour taste: ethanoic (acetic) acid or nitric acid?

    Ethanoic (acetic) acid

    Vinegar is a dilute aqueous solution of ethanoic (acetic) acid.

  4. 4. Which type of salt is always produced by reactions of sulfuric acid (H₂SO₄): a sulfate or a nitrate?

    Sulfate

    Sulfuric acid forms sulfate salts; nitric acid forms nitrates; hydrochloric acid forms chlorides.

  5. 5. What is the chemical test that confirms a gas is oxygen (O₂): it relights a glowing wooden splint, or it turns limewater milky?

    It relights a glowing wooden splint

    Pure oxygen supports rapid combustion and relights a glowing splint.

  6. 6. Which ion is released by all Arrhenius acids when dissolved in aqueous solution: hydrogen ions (H⁺) or hydroxide ions (OH⁻)?

    Hydrogen ions (H⁺)

    Acids produce aqueous hydrogen ions (H⁺ / H₃O⁺) in water.

  7. 7. On the standard pH scale (0 to 14) at 25 °C, what is the pH of a neutral solution such as pure water: 7 or 0?

    7

    A pH of 7 is neutral, with equal concentrations of H⁺ and OH⁻ ions.

  8. 8. Does an alkaline (basic) solution (such as sodium hydroxide or soapy water) have a pH greater than 7 or less than 7?

    Greater than 7

    Alkalis (soluble bases) have pH values above 7 (from 7 to 14).

  9. 9. What colour does blue litmus paper turn when dipped into an acidic solution: red or blue?

    Red

    Acids turn blue litmus paper red.

  10. 10. What are the two products formed when an acid reacts with an alkali in a neutralisation reaction: a salt and water, or hydrogen and carbon?

    A salt and water

    Acid + Alkali → Salt + Water (H⁺ + OH⁻ → H₂O).

  11. 11. Because the pH scale is logarithmic, a decrease of 1 pH unit (e.g. from pH 4 to pH 3) means the H⁺ ion concentration increases by a factor of: 10 or 2?

    10

    pH = −log₁₀[H⁺], so each whole unit decrease represents a tenfold increase in [H⁺].

  12. 12. What colour is phenolphthalein indicator in an acidic solution vs a basic solution: colourless in acid and pink in alkali, or blue in both?

    Colourless in acid and pink in alkali

    Phenolphthalein is colourless below pH 8.2 and turns pink-magenta in alkaline solutions.

12 questions · Seed 104729 · Age guidance, not curriculum certification